Engagement and/or homing of a surgical tool in a surgical robotic system

ABSTRACT

Engaging and/or homing is provided for a motor control of a surgical tool in a surgical robotic system. Where two or more motors are to control the same motion, the motors may be used to detect engagement even where no physical stop is provided. The motors operate in opposition to each other or in a way that does not attempt the same motion, resulting in one of the motors acting as a stop for the other motor in engagement. A change in motor operation then indicates the engagement. The known angles of engaged motors and the transmission linking the motor drives to the surgical tool indicate the home or current position of the surgical tool.

RELATED CASE

This application is a continuation of U.S. patent application Ser. No.16/661,590, filed Oct. 23, 2019, which is a continuation-in-part of U.S.patent application Ser. No. 15/999,561, filed Aug. 20, 2018, now U.S.Pat. No. 11,406,457, issued Aug. 9, 2022, the disclosures of which arehereby incorporated by reference in their entirety.

FIELD

Embodiments relate to control units for detecting the successfulengagement and/or homing of a surgical robotic tool with one or moreactuators in a surgical robotic arm of a surgical robotic system. Otherembodiments are also described.

BACKGROUND

Surgical robotic systems give an operator or user, such as an operatingsurgeon, the ability to perform one or more actions of a surgicalprocedure using the surgical robotic system. In the surgical roboticsystem, a surgical tool or instrument, such as an endoscope, clamps,cutting tools, spreaders, needles, energy emitters, etc., ismechanically coupled to a robot joint of a surgical robotic arm, so thatmovement or actuation of the robot joint directly causes a rotation,pivoting, or linear movement of a part of the tool (e.g., rotation of anendoscope camera, pivoting of a grasper jaw, or translation of aneedle). Once the tool is attached to (e.g., in contact with) a tooldrive in the arm, operator commands may cause movements and activatefunctions of the attached tool, such as closing clamps, adjusting thebend of an endoscope, extending an instrument outside of cannula walls,applying pressure using a clamping tool, as well as other movements andactions.

Due to the varied nature of surgical procedures, different surgicaltools or instruments may be selectively attached to the same arm of asurgical robotic system before and during a surgical procedure. In orderto avoid equipment malfunctions during a surgical procedure, it isimportant that the surgical tool or instrument not only be attached tobut also engaged in a mechanical sense to the robot joint of thesurgical robotic arm. That is, mechanisms in the surgical tool thatimpart motion or enable the activation of instrument features (e.g.,opening, closing, cutting, applying pressure, etc.), should bemechanically engaged to the actuators that are in the tool drive of thearm of the surgical robotic system, before the surgical tool is in useduring the surgical procedure.

SUMMARY

By way of introduction, the preferred embodiments described belowinclude methods, systems, instructions, and computer readable media forengaging and/or homing of a motor control of a surgical tool in asurgical robotic system. Where two or more motors are to control thesame motion, the motors may be used to detect engagement even where nophysical stop is provided. The motors operate in opposition to eachother or in a way that does not attempt the same motion, resulting inone of the motors acting as a stop for the other motor in engagement. Achange in motor operation then indicates the engagement. The knownangles of engaged motors and the transmission linking the motor drivesto the surgical tool indicate the home or current position of thesurgical tool.

In a first aspect, a method is provided for engaging motor control of asurgical tool in a surgical robotic system. First and second motorsconnected with first and second drive discs, respectively, are rotated.The first and second drive discs are in contact with first and secondtool discs. Both the first and second tool discs are linked to thesurgical tool. The first and second motors rotate such that the firstand second drive discs rotate in opposition to each other for movementof the surgical tool. Engagement of the first and second motors with thefirst and second discs, respectively, is detected from a change inperformance of the first and second motors.

In a second aspect, a surgical robotic system is provided for engagementof motor control in a robotic surgery system. A surgical tool connectsby a transmission to first and second rotary tool pads. The surgicaltool connects such that rotation of the first and second rotary toolpads rotates the surgical tool. A tool drive has first and second rotarydrives mateable with the first and second rotary tool pads. A processoris configured to detect mating of the first and second rotary tool padswith the first and second rotary drives by a change in a signal.

In a third aspect, a method is provided for homing a rotational positionof a surgical tool in a surgical robotic system. Engagement of first andsecond rotary tool pads with first and second rotary drives is detected.A rotation angle of the surgical tool linked to the first and secondrotary tool pads is determined from first and second rotation angles ofthe first and second rotary drives once the engagement is detected.

The present invention is defined by the following claims, and nothing inthis section should be taken as a limitation on those claims. Furtheraspects and advantages of the invention are discussed below inconjunction with the preferred embodiments and may be later claimedindependently or in combination.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the invention are illustrated by way of example andnot by way of limitation in the figures of the accompanying drawings inwhich like references indicate similar elements. It should be noted thatreferences to “an” or “one” embodiment of the invention in thisdisclosure are not necessarily to the same embodiment, and they mean atleast one. Also, in the interest of conciseness and reducing the totalnumber of figures, a given figure may be used to illustrate the featuresof more than one embodiment of the invention, and not all elements inthe figure may be required for a given embodiment.

FIG. 1 is a pictorial view of an example surgical robotic system in anoperating arena;

FIG. 2 is an illustration of a system for detecting engagement of asurgical tool to a tool drive of a surgical robotic arm;

FIG. 3 is a block diagram showing a surgical tool, a tool drive, and acontrol unit;

FIGS. 4A-4C illustrate different states of a tool disk and a drive diskduring an engagement process;

FIG. 5A is a flow diagram illustrating a process performed by a controlunit for engaging a surgical tool with a tool drive;

FIG. 5B is a flow diagram illustrating another process for a controlunit detecting engagement of a tool disk to a drive disk based on one ormore operating parameters of an actuator that is driving the drive disk;

FIG. 5C is a flow diagram illustrating another process for a controlunit to detect engagement of a surgical tool with a tool drive of asurgical robotic system;

FIG. 6 depicts a block diagram of a feedback loop; and

FIG. 7 depicts a block diagram of a controller for use in a feedbackloop.

FIG. 8 illustrates an example of the rotational angle relationshipsbetween motors and corresponding drive discs, tool discs, and a surgicaltool.

FIG. 9 illustrates one embodiment of a drive current used forengagement.

FIG. 10 is a flow diagram illustrating another process for a controlunit detecting engagement and/or for homing.

DETAILED DESCRIPTION

Embodiments of an apparatus, system and method for detection ofengagement of a detachable surgical robotic tool to a tool drive of asurgical robotic arm of a surgical robotic system are described herein.In the following description numerous specific details are set forth toprovide a thorough understanding of the embodiments. One skilled in therelevant art will recognize, however, that the techniques describedherein can be practiced without one or more of the specific details, orwith other methods, components, materials, etc. In other instances,well-known structures, materials, or operations are not shown ordescribed in detail to avoid obscuring certain aspects.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearances of the phrases “in one embodiment” or “in an embodiment” invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics such as those shown in different drawingsmay be combined in any suitable manner in one or more embodiments.

Referring to FIG. 1 , this is a pictorial view of an example surgicalrobotic system 100 in an operating arena. The surgical robotic system100 includes a user console 102, a control tower 103, and one or moresurgical robotic arms 104 at a surgical platform 105, e.g., a table, abed, etc. The surgical robotic system 100 can incorporate any number ofdevices, tools, or accessories used to perform surgery on a patient 106.For example, the surgical robotic system 100 may include one or moresurgical tools 107 used to perform surgery. The surgical tool 107 mayhave an end effector at its distal end (also a distal end of the roboticsurgical arm 4 to which the surgical tool 107 is attached), forexecuting a surgical operation such as cutting, grasping, poking, orenergy emission.

Each surgical tool 107 may be manipulated manually, robotically, orboth, during the surgery. For example, the surgical tool 107 may be atool used to enter, view, or manipulate an internal anatomy of thepatient 106. In an embodiment, the surgical tool 106 is a grasper thatcan grasp tissue of the patient. The surgical tool 106 may be controlledmanually, directly by a hand of a bedside operator 108; or it may becontrolled robotically, via sending electronic commands to actuatemovement of the surgical robotic arm 104 to which the surgical tool 106is attached. The surgical robotic arms 104 are shown as a table-mountedsystem, but in other configurations the surgical robotic arms 104 may bemounted in a cart, ceiling or sidewall, or in another suitablestructural support.

Generally, a remote operator 109 such as a surgeon may use the userconsole 102 to remotely manipulate the surgical robotic arms 104 and theattached surgical tools 107, e.g., teleoperation. The user console 102may be located in the same operating room as the rest of the surgicalrobotic system 100, as shown in FIG. 1 . In other environments however,the user console 102 may be located in an adjacent or nearby room, or itmay be at a remote location, e.g., in a different building, city, orcountry. The user console 102 may comprise a seat 110, foot-operatedcontrols 113, one or more handheld user interface devices, UID 114, andat least one user display 115 that is configured to display, forexample, a view of the surgical site inside the patient 106. In theexample user console 102, the remote operator 109 is sitting in the seat110 and viewing the user display 115 while manipulating a foot-operatedcontrol 113 and a handheld UID 114 in order to remotely control thesurgical robotic arms 104 and the surgical tools 107 (that are mountedon the distal ends of the surgical arms).

In some variations, the bedside operator 108 may also operate thesurgical robotic system 100 in an “over the bed” mode, in which thebeside operator 108 (user) is now at a side of the patient 106 and issimultaneously manipulating i) a robotically-driven tool (having an endeffector) that is attached to the surgical robotic arm 104, e.g., with ahandheld UID 114 held in one hand, and ii) a manual laparoscopic tool.For example, the bedside operator's left hand may be manipulating thehandheld UID to control a surgical robotic component, while the bedsideoperator's right hand may be manipulating a manual laparoscopic tool.Thus, in these variations, the bedside operator 108 may perform bothrobotic-assisted minimally invasive surgery and manual laparoscopicsurgery on the patient 106.

During an example procedure (surgery), the patient 106 is prepped anddraped in a sterile fashion to achieve anesthesia. Initial access to thesurgical site may be performed manually while the arms of the surgicalrobotic system 100 are in a stowed configuration or withdrawnconfiguration (to facilitate access to the surgical site.) Once accessis completed, initial positioning or preparation of the surgical roboticsystem 100 including its surgical robotic arms 104 may be performed.Next, the surgery proceeds with the remote operator 109 at the userconsole 102 utilizing the foot-operated controls 113 and the UIDs 114 tomanipulate the various end effectors and perhaps an imaging system toperform the surgery. Manual assistance may also be provided at theprocedure bed or table, by sterile-gowned bedside personnel, e.g., thebedside operator 108 who may perform tasks such as retracting tissues,performing manual repositioning, and tool exchange upon one or more ofthe surgical robotic arms 104. Non-sterile personnel may also be presentto assist the remote operator 109 at the user console 102. When theprocedure or surgery is completed, the surgical robotic system 100 andthe user console 102 may be configured or set in a state to facilitatepost-operative procedures such as cleaning or sterilization andhealthcare record entry or printout via the user console 102.

In one embodiment, the remote operator 109 holds and moves the UID 114to provide an input command to move a robot arm actuator 117 in thesurgical robotic system 100. The UID 114 may be communicatively coupledto the rest of the surgical robotic system 100, e.g., via a consolecomputer system 116. The UID 114 can generate spatial state signalscorresponding to movement of the UID 114, e.g. position and orientationof the handheld housing of the UID, and the spatial state signals may beinput signals to control a motion of the robot arm actuator 117. Thesurgical robotic system 100 may use control signals derived from thespatial state signals, to control proportional motion of the actuator117. In one embodiment, a console processor of the console computersystem 116 receives the spatial state signals and generates thecorresponding control signals. Based on these control signals, whichcontrol how the actuator 117 is energized to move a segment of thesurgical robotic arm 104, the movement of a corresponding surgical toolthat is attached to the arm may mimic the movement of the UID 114.Similarly, interaction between the remote operator 109 and the UID 114can generate for example a grip control signal that causes a jaw of agrasper of the surgical tool 107 to close and grip the tissue of patient106.

Surgical robotic system 100 may include several UIDs 114, whererespective control signals are generated for each UID that control theactuators and the surgical tool (end effector) of a respective surgicalrobotic arm 104. For example, the remote operator 109 may move a firstUID 114 to control the motion of an actuator 117 that is in a leftrobotic arm, where the actuator responds by moving linkages, gears,etc., in that surgical robotic arm 104. Similarly, movement of a secondUID 114 by the remote operator 109 controls the motion of anotheractuator 117, which in turn moves other linkages, gears, etc., of thesurgical robotic system 100. The surgical robotic system 100 may includea right surgical robotic arm 104 that is secured to the bed or table tothe right side of the patient, and a left surgical robotic arm 104 thatis at the left side of the patient. An actuator 117 may include one ormore motors that are controlled so that they drive the rotation of ajoint of the surgical robotic arm 104, to for example change, relativeto the patient, an orientation of an endoscope or a grasper of thesurgical tool 107 that is attached to that arm. Motion of severalactuators 117 in the same surgical robotic arm 104 can be controlled bythe spatial state signals generated from a particular UID 114. The UIDs114 can also control motion of respective surgical tool graspers. Forexample, each UID 114 can generate a respective grip signal to controlmotion of an actuator, e.g., a linear actuator, that opens or closesjaws of the grasper at a distal end of surgical tool 107 to grip tissuewithin patient 106.

In some aspects, the communication between the surgical platform 105 andthe user console 102 may be through a control tower 103, which maytranslate user commands that are received from the user console 102 (andmore particularly from the console computer system 116) into roboticcontrol commands that are transmitted to the surgical robotic arms 104on the surgical platform 105. The control tower 103 may also transmitstatus and feedback from the surgical platform 105 back to the userconsole 102. The communication connections between the surgical platform105, the user console 102, and the control tower 103 may be via wiredand/or wireless links, using any suitable ones of a variety of datacommunication protocols. Any wired connections may be optionally builtinto the floor and/or walls or ceiling of the operating room. Thesurgical robotic system 100 may provide video output to one or moredisplays, including displays within the operating room as well as remotedisplays that are accessible via the Internet or other networks. Thevideo output or feed may also be encrypted to ensure privacy and all orportions of the video output may be saved to a server or electronichealthcare record system.

FIG. 2 is an illustration of a subsystem or a part of the surgicalrobotic system 100, for detecting engagement of a surgical tool 240 to atool drive 230 of a surgical robotic arm 220. The surgical robotic arm220 may be one of the surgical robotic arms 104 of surgical roboticsystem 100 illustrated and discussed with respect to FIG. 1 . Thecontrol unit 201 may be part of for example the control tower in FIG. 1. As discussed in more detail herein, the engagement may be detected bycontrol unit 210 based on one or more motor operating parameters of oneor more actuators (e.g., actuator 238-j) in the tool drive 230.

There is a tool drive 230 to which different surgical tools (e.g.,surgical tool 240, as well as other detachable surgical tools—not shown)may be selectively attached (one at a time.) This may be done by forexample a human user holding the housing of the surgical tool 240 in herhand and moving the latter in the direction of arrow 280 shown until theoutside surface of the surgical tool 240 in which there are one or moretool disks (e.g., tool disk 244-i) comes into contact with the outsidesurface of the tool drive 230 in which there are one or more drive disks(e.g., drive disk 234-j). In the example shown, the tool drive 230 is asegment of the surgical robotic arm 220 at a distal end portion of thesurgical robotic arm 220. A proximal end portion of the arm 220 issecured to a surgical robotic platform, such as a surgical table that isnot shown in FIG. 2 but an example of which may be seen in FIG. 1described above.

Control unit 210 is responsible for controlling motion of the variousmotorized joints in the surgical robotic arm 220 (including the drivedisks 234) through which operation of end effector 246 (its position andorientation as well as its surgical function) which mimics that of auser input device is achieved. This is achieved via a mechanicaltransmission in the surgical tool 240, when the surgical tool 240 hasbeen engaged to transfer force or torque from the tool drive 230. Thecontrol unit 210 may be implemented as a programmed processor, forexample as part of the control tower 103 of FIG. 1 . It may respond toone or more user commands received via a local or remote user input(e.g., joystick, touch control, wearable device, or other user inputdevice communicating via console computer system 116.) Alternatively,the control unit 210 may respond to one or more autonomous commands orcontrols (e.g., received form a trained surgical machine learning modelthat is being executed by the control unit 210 or by the consolecomputer system 116), or a combination thereof. The commands dictate themovement of robotic arm 220 and operation of its attached end effector246.

The end effector 246 may be any surgical instrument, such as jaws, acutting tool, an endoscope, spreader, implant tool, etc. Differentsurgical tools each having different end effectors can be selectivelyattached (one at a time) to robotic arm 220 for use during a surgical orother medical procedure. The end effector 246 depicted in the example ofFIG. 2 is jaws located at a distal end of the surgical tool 240 and thatmay be retracted into, or extend out of, a cannula as shown (e.g., athin tube that may be inserted into a patient undergoing a surgicalprocedure).

The robotic arm 220 includes a tool drive 230, in which there are one ormore actuators, such as actuator 238-j. Each actuator may be a linear orrotary actuator that has one or more respective electric motors (e.g., abrushless permanent magnet dc motor) whose drive shaft may be coupled toa respective drive disk 234-j through a transmission (e.g., a gear trainthat achieves a given gear reduction ratio—not shown). The tool drive230 includes one or more drive disks 234 that may be arranged on aplanar or flat surface of the tool drive 230, wherein the figure showsseveral such drive disks that are arranged on the same plane of the flatsurface. Each drive disk (e.g., drive disk 234-j) is exposed on theoutside surface of the tool drive 230 and is designed to mechanicallyengage (e.g., to securely fasten via snap, friction, or other matingfeatures) a mating tool disk 244-j of the surgical tool 240, to enabledirect torque transfer between the two. This may take place once forexample a planar or flat surface of the surgical tool 240 andcorresponding or mating planar or flat surface of the tool drive 230 arebrought in contact with one another.

Furthermore, a motor driver circuit (not shown but that may for examplebe installed in the tool drive 230 or elsewhere in the surgical roboticarm 220) is electrically coupled to the input drive terminals of aconstituent motor of one or more of the actuators 238. The motor drivercircuit manipulates the electrical power drawn by the motor in order toregulate for example the speed of the motor or its torque, in accordancewith a motor driver circuit input, which can be set or controlled bycontrol unit 210, which results in the powered rotation of theassociated drive disk (e.g., drive disk 234-j).

When the mating drive disk 234-j is mechanically engaged to a respectivetool disk 244-j, the powered rotation of the drive disk 234-j causes thetool disk 244-j to rotate, e.g., the two disks may rotate as one,thereby imparting motion on, for example, linkages, gears, cables,chains, or other transmission means within the surgical tool 240 forcontrolling the movement and operation of the end effector 246 which maybe mechanically coupled to the transmission means.

Different surgical tools may have different numbers of tool disks basedon the types of movements and the number of degrees of freedom in whichthe movements are performed by their end effectors, such as rotation,articulation, opening, closing, extension, retraction, applyingpressure, etc.

Furthermore, within the surgical tool 240, more than one tool disk 244may contribute to a single motion of the end effector 246 to achievegoals such as load sharing by two or more motors that are driving themating drive disks 234, respectively.

In another aspect, within the tool drive 230, there may be two or moremotors whose drive shafts are coupled (via a transmission) to rotate thesame output shaft (or drive disk 234), to share a load.

In yet another aspect, within the surgical tool 240, there may be atransmission which translates torque from two drive disks 234 (viarespective tool disks 244) for performing complimentary actions in thesame degree of freedom, e.g., a first drive disk 234-i rotates a drumwithin the housing of the surgical tool 230 to take in one end of acable, and a second drive disk 234-j rotates another drum within thehousing of the surgical tool 230 to take in the other end of the cable.As another example, the extension and the shortening of an end effectoralong a single axis may be achieved using two tool disks 234-i, 234-j,one to perform the extension and another to perform the retraction, forexample via different cables. This is in contrast to an effector thatalso moves in one degree of freedom (e.g., extension and shorteninglongitudinally along a single axis of movement) but that only needs asingle tool disk to control its full range of movement. As anotherexample, an effector that moves in multiple degrees of freedom (e.g.,such as a wristed movement, movement along multiple axes, activation ofan energy emitter in addition to end effector movement, etc.) maynecessitate the use of several tool disks (each being engaged to arespective drive disk). In another type of surgical tool 240, a singletool disk 244 is sufficient to perform both extension and retractionmotions, via direct input (e.g., gears). As another example, in the caseof the end effector 246 being jaws, two or more tool disks 244 maycooperatively control the motion of the jaws, for load sharing, asdiscussed in greater detail herein.

In some embodiments, when surgical tool 240 is first attached to orinstalled on tool drive 230 such that the tool disks are broughtsubstantially into coplanar and coaxial alignment with correspondingdrive disks (though the tool and drive disks are perhaps not yetsuccessfully engaged), control unit 210 initially detects the type ofthe surgical tool 240. In one embodiment, surgical tool 240 has aninformation storage unit 242, such as a solid state memory, RFID tag,bar code (including two-dimensional or matrix barcodes), etc., thatidentifies its tool or end effector information, such as one or more ofidentification of tool or end effector type, unique tool or end effectorID, number of tool disks used, location of those tool disks being used(e.g., from a total of six possible tool disks 244-e, f, g, h, i, j),type of transmission for the tool disks (e.g., direct drive, cabledriven, etc.), what motion or actuation a tool disk imparts on the endeffector, one or more tool calibration values (e.g., a rotationalposition of the tool disk as determined during factor testing/assemblyof the tool), whether motion of the end effector is constrained by amaximum or minimum movement, as well as other tool attributes. In oneembodiment, the information storage unit 242 identifies minimalinformation, such as a tool ID, which control unit 210 may use toperform a lookup of the various tool attributes.

The tool drive 230 may include a communication interface 232 (e.g., amemory writer, a near field communications, NFC, transceiver, RFIDscanner, barcode reader, etc.) to read the information from theinformation storage unit 242 and pass the information to control unit210. Furthermore, in some embodiments, there may be more than oneinformation storage unit in surgical tool 240, such as one informationstorage unit associated with each tool disk 244. In this embodiment,tool drive 230 may also include a corresponding sensor for each possibleinformation storage unit that would be present in a given tool.

Engagement

After surgical tool 240 is attached with tool drive 230, such that tooldisks are brought into alignment and are superimposed on correspondingdrive disks (although not necessarily mechanically engaged), and afterthe tool disk information is obtained, e.g., read by control unit 210,the control unit 210 performs an engagement process to detect when allof the tool disks that are expected to be attached to respective drivedisks are mechanically engaged with their respective drive disks (e.g.,their mechanical engagement has been achieved, or the tool drive is nowdeemed engaged with the tool). That is, attaching the surgical tool 240with the tool drive 230 does not necessarily ensure the proper matingneeded for mechanical engagement of tool disks with corresponding drivedisks (e.g., due to misalignment of mating features). The engagementprocess may include activating one or more motors of an actuator (e.g.,actuator 238-j) that drives a corresponding drive disk 234-j. Then,based on one or more monitored motor operating parameters of theactuator 238-j, while the latter is driving the drive disk 234-j, themechanical engagement of the tool disk 244-i with a drive disk 234-j canbe detected, as discussed in greater detail below. This process may berepeated for every drive disk 234 (of the tool drive 230) that isexpected to be currently attached to a respective tool disk 244 (e.g.,as determined based on the tool disk information obtained for theparticular surgical tool 240 that is currently attached.)

Upon detecting that a particular type of surgical tool 240 has beenattached with the tool drive 230, the control unit 210 activates one ormore actuators (e.g., motors) of the tool drive 230 that have beenpreviously associated with that type of surgical tool 240. In someembodiments, each actuator that is associated with a corresponding drivedisk 234 of surgical tool 240 may be activated simultaneously, serially,or a combination of simultaneous and serial activation. FIG. 3illustrates an example of the surgical tool 240 that utilizes four tooldisks, such as tool disk 244-i, arranged in a coplanar fashion on amating surface of its housing. Each tool disk contributes to at least aportion of the movement and/or activation of end effector 246. Upondetecting the attachment of surgical tool 240 with tool drive 230 (e.g.,joining of mating surfaces of the respective housings), control unit 210(or its processor 312 while executing instructions stored in memory 314as engagement control 316) performs a process which determines that onlythe corresponding four drive disks, such as drive disk 234-j, need to beturned (a corresponding actuator 238-j needs to be activated—see FIG. 2) to perform the engagement process.

Returning to FIG. 2 , during operation of actuator 238-j, after thedetected attachment of surgical tool 240 with tool drive 230, one ormore sensors 236-j measure one or more motor operating parameters of theactuator 238-j as its motor is signaled to start to move. In oneembodiment, the actuator 238-j will turn in a direction that causes itsattached (though not yet engaged) tool disk 244-i to wind a cable in thetransmission housing of the tool 240, for cable driven surgical tools.As an example, see FIG. 4A in which motion 445 of the tool disk 244avoids unwinding of cable 446, and thereby holds the tool disk 244 inplace or starts to turn the tool disk 244 in the direction of motion 445(which winds the cable 446.) This turning of the tool disk 244 continuesuntil engagement is achieved as explained further below in connectionwith FIG. 4B and FIG. 4C.

In another embodiment, the selected actuator is signaled to turn so asto cause its attached tool disk 244 to rotate so that the end effector246 that is connected to the tool disk 244 moves towards a physicalconstraint (e.g. a jaw opens until it stops against a cannula wall, amaximum in a range of motion is achieved when bumping against a hardstop in a fully open position, etc.) In yet another embodiment, such asan endoscope embodiment where two actuators are sharing the load beingrotation of an endoscope camera where there may be no hard stops againstrotation of the camera, the selected actuator rotates its attached tooldisk 244-i in a direction that opposes the motion of another tool disk244-j that is also rotatably coupled to the same output shaft in thetransmission housing of the tool 240. In that instance, as soon as oneof the tool disks 244-i, 244-j engages, it will act as a physicalconstraint to the other tool disk. Other predetermined directions ofmovement may also be used consistent with the discussion herein.

Furthermore, in some embodiments, the actuator's movement is ramped orincreased gradually by the control unit 210 (e.g., the control unit 210signals or commands the actuator to start to rotate at a slow speed atthe beginning of movement and then progressively increase the speed, andthen progressively decrease the speed at detection of engagement).

In one embodiment, the calibration values stored in the informationstorage unit 242 of the surgical tool 246 may be used to expedite toolengagement. For example, the calibration values can include a factorydetermined position (angle) of a particular tool disk 244-j, recordedduring product assembly or testing. The engagement process may need tohave knowledge of a home position of a corresponding drive disk 234-j.This knowledge may be obtained by the control unit 210 performing a tooldriver calibration routine, in which it determines when a particulardrive disk 234-j has reached a home position (as the control unitactuates the drive disk 234-j), such that position of that drive disk234-j is now known by the control unit 210. Note that the control unit210 may do so while only relying on output from a position sensor thatis in the tool drive 230, and the tool 240 itself may be passive in thatit has no electronic sensors in it.

Next, the control unit 210 may activate the corresponding actuator ofthe drive disk 234-j so that the drive disk 234-j turns at a high speeduntil a position variable of the drive disk 234-j comes close to thefactory determined position. When the drive disk satisfies a thresholddistance relative to the factory determined position (e.g., a homeposition of the tool disk) which implies that mating features of thetool disk and drive disk are near alignment, the speed may be reduced soas to increase the likelihood that the mating features will engage oneanother upon their initial encounter. This process may work for bothdirect transmissions as well as for tool disks that utilize a cable todrive the effector (as in FIG. 4A.) For the latter, the calibrationvalue may include a rotation count (e.g., a number of complete rotationsof a motor drive shaft) that can be used to limit the continued turningof the drive disk 234-j once engagement has been detected, to ensurethat a maximum length of winding of the cable is not exceeded, or anangle of rotation of the engaged, tool disk 244-j and drive disk 234-jis not exceeded.

In some embodiments, the motor operating parameters monitored by thecontrol unit 210 (via sensors 236) are interpreted to mean successfulmechanical engagement of a tool disk with a drive disk. These caninclude measurements of torque applied by the actuator 238-j as measuredby a torque or force sensor, measurements of current supplied to a motorof the actuator 238-j when attempting to drive the actuator to move at acertain velocity (e.g., where the sensor 236-j may include a currentsensing resistor in series with a motor input drive terminal),measurements of electrical impedance as seen into the input driveterminals of the motor of the actuator when attempting to drive themotor to move at a certain velocity (e.g., where the sensor 236-j mayalso include a voltage sensing circuit to measure voltage of the motorinput drive terminal), speed of the actuator 238-j (e.g., where thesensor 236-j may include a position encoder (sensor) on an output shaftof the actuator 238-j or on a drive shaft of the motor), as well asother parameters referred to here as motor operating parameters. Whilemonitoring the one or more motor operating parameters of a particularactuator, when one or more of these parameters satisfies (e.g., meets orreaches) a predetermined, condition or threshold, the detection of sucha situation can be interpreted by control unit 210 as a mechanicalengagement event. Note that satisfying the predetermined condition mayfor example mean that the monitored operating parameter exhibits certainchanges, as per the threshold, relative to an operating parameter ofanother motor that is part of the same actuator 238-j or that is part ofanother actuator 238-i which his being controlled by the control unit210 simultaneously during the engagement detection process.

In some embodiments, detection of certain motor operating parametersduring operation of the actuator 238-j, such as one or more of i) torquethat satisfies (e.g., rises and reaches) a torque threshold, ii) motorcurrent that satisfies (e.g., rises and reaches) a current threshold,iii) impedance that drops below an impedance threshold, iv) motor speeddropping below a motor velocity threshold, or a combination thereof, areused by control unit 210 to determine that mechanical engagement of tooldisk 244-j to drive disk 234-j has occurred. The following are someexamples of such a process.

In one embodiment, where the tool disk 244-j uses a cable 446 to controlmovement of its end effector 246, the actuator 238-j (that is drivingthe corresponding drive disk 234-j) will move in the direction thatwinds the cable (here, the direction of motion 445 of which the controlunit 210 may have knowledge, based on having previously identified thetype of tool 240). FIG. 4A depicts such a tool disk 244 that has a pairof coupling features 447 a, 447 b on its disk face, which are depictedas hollow circles. Each coupling feature 447 a, 447 b may be a separate,cylindrical cavity formed in the disk face. The direction of motion 445will wind the cable 446 around it, where in this initial condition thecable 446 has some slack as shown that will disappear as the cable 446is being wound in the direction of motion 445.

A drive disk 234 is concentrically aligned with the tool disk 244, asseen in FIG. 4B. That is, FIG. 4B illustrates drive disk 234 aligned andsuperimposed over the tool disk 244 such that their respective diskfaces are brought into contact with one another. The drive disk 234 hasa pair of coupling features 448 a, 448 b on its disk face, depicted assolid circles. Each coupling feature 448 a, 448 b may be a separate,cylindrical pin formed on the disk face. In this particular example,each of the coupling features 448 is sized to easily fit into either ofthe features 447 (once the two complementary features are aligned.) InFIG. 4B, the features 447 a, 447 b and the features 448 a, 448 b aremisaligned even though the faces of their respective tool and drivedisks are in contact with one another. In other words, in FIG. 4B one ormore mating or complementary pairs of features, such as features 447a-448 a, or features 447 a-448 b, are not yet mechanically engaged witheach other. During such a condition, the drive disk 234 continues to bedriven by its actuator 238, to move (turn) in the direction of movement445 until mechanical engagement is reached in the condition depicted inFIG. 4C.

As illustrated in FIG. 4C, the drive disk 234 while turning has reachedthe point where both the coupling features 447 a-448 a and the couplingfeatures 447 b-448 b have mechanically engaged each other as shown sothat they now move as one (if the drive disk 234 continues to turn.) Inthe example here, each pin-cavity pair is now interlocked as shown inthis figure. In addition, at this point the cable 446 is now taughtafter having been wound, and may thus serve to help hold the tool disk244 in place (prevents its rotation) as drive disk 234 continues to turnin the direction of motion 445. Further turning of the drive disk 234 inthe condition of FIG. 4C may increase tension in the cable 446 as thecable 446 pulls on its end effector 246 until a hard stop is reachedwhich creates a physical constraint against further movement in thedirection of movement 445 of the now-engaged drive disk 234.

The physical constraint on further turning of the drive disk 234 enablesdetection of the mechanical engagement event, by the control unit 210making its measurement of motor operating parameters and comparison toone or more thresholds that may have been predetermined to be indicativeof engagement. For example, the velocity/speed of the motor droppingbelow one or more threshold values indicates engagement because themotor is constrained from further movement in the winding direction. Asanother example, engagement occurs when the torque applied by the motorincreases to a value greater than a freely moving motor and/or greaterthan the friction that results from tool disks and drive disks and/orattachment features rubbing or sliding against one another beforeengagement. Similarly, in other embodiments, the measured current and/orimpedance approaches and may reach a maximum predetermined value whenengagement occurs and as power is continued to be supplied to a motor inan attempt to continue movement of the drive disk in the predetermineddirection. When one or more of these thresholds are satisfied, controlunit 210 can conclude that engagement has occurred between a tool diskand a drive disk.

Other forms of physical constraint can be used by control unit 210 fordetecting successful drive disk and tool disk engagement. For example, amotion constraint, such as a mechanical limit of a range of motionimposed by a joint of the end effector (e.g., a joint that can onlyrotate about an axis from −45 to 45 degrees) or a physical barrier tomovement (e.g., a cannula wall that impedes movement of the endeffector), may also be utilized as the physical constraint/hard stopdiscussed above for either cable driven or non-cable driven tools.

In some embodiments, the surgical tool 240 may not have a physicalconstraint/hard stop in at least one degree of freedom of movement fromwhich motor operating parameters can be measured. For example, a tooldisk 244-j may be responsible for imparting unconstrained rotation ofthe end effector 246 element about an axis. Even with such unconstrainedmovement however, the control unit 210 may still detect engagement ofthe drive disk 234-j to the tool disk 244-j by detecting changes in oneor more motor operating parameters during the engagement detectionprocess. For example, a motor operating parameter pattern, such asrepeating torque spikes caused by the features 447 rotating past thefeatures 488 (and thus not engaging each other) is indicative of lack ofengagement. Accordingly, the stopping or non-existence of that torquespike pattern (while the drive disk 234-j continues to turn) means thatthe control unit 210 has detected tool disk to drive disk engagement.

In some embodiments, a physical constraint may be created by the use ofcoordinating movement of multiple drive disks, and/or by letting asingle drive disk engage before engaging a second drive disk. Forexample, consider the case where two or more tool disks (in the samehousing of a surgical tool 240) are connected by a transmission in thehousing of the tool 240 to share a load (end effector 246) when turningin the same direction, such as when a cutting or clamping tool may needto apply force beyond that which a single actuator 238-j could supply.In such an embodiment, two or more actuators that are turning in thesame direction (their respective drive disks are turning in the samedirection) are driving the same output shaft that is inside the surgicaltool 240 (due to the transmission in the surgical tool 240 that isconnected to the corresponding tool disks.) Now, if the two actuatorsare signaled to move in opposing directions, then as soon as one of thedrive disks engages its corresponding tool disk, this becomes a physicalconstraint to the other drive disk (when the other drive disk hasengaged its corresponding tool disk.) When one of the two or moreactuators engages (its drive disk engages its corresponding tool disk),the control unit 210 creates a constraint for the other actuator bysignaling the engaged actuator to, for example, enter a position holdstate. That is, a first actuator 238-j will be commanded by the controlunit 210 to hold its position while the other, non-engaged actuator238-i continues to be signaled to drive and thus turn or move (towardengagement between its drive disk 234-i and tool disk 244-i.) In thisembodiment, one or both of the actuators' motor operating parameters canbe monitored to detect engagement between a tool disk and drive diskpair. Furthermore, if a hard stop does exist (the control unit 210expects or knows that this particular tool 240 has a hard stop), thenthe actuator of an engaged drive disk can be signaled to continue todrive or turn in the same direction until the hard stop is detected. Theother actuator may continue to turn in the opposing direction andattempt to engage while the already engaged actuator holds its positionat the hard stop.

Returning to FIG. 2 , and as discussed above, the tool identificationperformed by control unit 210 enables the latter to get knowledge of thecharacteristics of the end effector 246 of surgical tool 240. Forexample, the control unit 210 may use that identification process todetermine whether two (or more) tool disks in the tool 240 act inconcert to impart end effector movement, whether one or more movementsof the end effector are subject to hard stops or physical constraints,what are the ranges of movement of the end effector, what actuators willbe used by the tool 240, and factory defined calibration values such asa home position of a tool disk. Note that a calibration value mayencompass a range, e.g., 290 degrees+/−4 degrees. Based on such acalibration value, e.g., a home position of the tool disk 244-i, andbased on the present position of the corresponding drive disk 234-i(determined using a position encoder in the tool drive 230), the controlunit 210 can track the difference during the engagement process (as theactuator is signaled to turn.) So long as the difference is greater thana predetermined threshold, then the actuator is signaled to turn rapidly(fast rotation), and then in response to the difference becoming smallerthan the threshold (implying that the drive disk is nearing thecalibration value home position) the actuator is signaled to turn slowly(slow rotation). And that is expected to increase the chances of areliable engagement being detected.

In some embodiments, after an engagement is detected by control unit210, control unit 210 may take one or more additional actions withrespect to the end effector 246 to confirm the engagement. For example,control unit 210 may subject the end effector to a predetermined set ofone or more motions to test the engagement, such as signaling a drivedisk to reverse direction thereby moving end effector in an oppositedirection to what it was doing during the engagement process, moving theend effector to achieve an expected maximum degree of movement, etc.Such movements enable control unit 210 to for example reach a hard stopor reach a physical constraint again, which is detected as discussedherein based on one or more motor operating parameters, to confirmmechanical engagement between the tool disks and drive disks.

Furthermore, in some embodiments, control unit 210 may utilize the hardstop or physical constraint to set a reference position of the endeffector. For example, knowing that a hard stop is to occur when the endeffector reaches 270° of rotation in a certain direction, control unit210 can set calibration values for a position of the correspondingactuator or drive disk. Then, movement of the actuator or drive disk canbe tracked based on number of rotations of the drive disk, motor shaft,gear ratio, drive disk/motor indexing, etc.

Furthermore, in some embodiments, control unit 210 may signal actuationby one or more motors for a specified number of times, a specifiednumber of rotations, or a combination thereof, when attempting toachieve engagement of tool disks with drive disks. When engagement isnot achieved within a threshold amount of time, number of rotations,etc. control unit 210 may issue a warning to an operator of the surgicalrobotic system (e.g., an operator of system 100 of FIG. 1 ) to detachand then reattach surgical tool 240 to restart the engagement process.

After mechanical engagement of drive disks with tool disks is detectedby control unit 210, an operator may command motions of one or morejoints of surgical robotic arm 220. As discussed above, the commands arereceived from or originate from one or more UIDs (e.g., UID 114), asspatial state signals from the UIDs which are translated tocorresponding control signals that the control unit 210 provides (e.g.,a desired motor speed or current and direction of rotation) to energizeone or more actuators of tool drive 230 which will change the pose,position or other state of the end effector. In one embodiment, wheretwo or more actuators are cooperatively controlling the motion of theend effector, such as when two or more tool disks are to impart motionof the end effector in the same degree of freedom, control unit 210further performs a cooperative control technique to ensure that theactuators operate in a complementary fashion when moving the endeffector, share a load associated with movement of the end effector, donot fight one another in imparting such motion, maintain a balancebetween the actuators so that one actuator does not continually performmore or less work than the other actuators, etc. For example, when twoor more actuators are used to control the opening, closing, andapplication of grip force of jaws of the end effector 246, control unitutilizes a multi-actuator operation control technique that identifies afirst of the two or more actuators as a master actuator, and theremaining one or more actuators as slave actuators. Then, a positioncommand that has been provided to signal the master actuator to move theend effector 246 to a commanded position, is also provided to signal theslave actuator to move the end effector 246 to the same commandedposition. For instance, if the master actuator and the slave actuatorare replicates, then if the master actuator receives a certain polarity(direction of rotation of its motor) and a certain motor current valueto satisfy a given end effector position command, the same polarity andcurrent value may also be supplied to each of the slave actuators. Insome embodiments however, there may be some compensation for how motionof the actuators complement each other, for example, reversing polarityfor the slaves when rotation directions of master and slave actuatorsare different, adjusting gain (e.g., of the commanded motor current)when attributes of the motors are different, etc., as discussed ingreater detail herein.

FIG. 3 is a block diagram showing an example of the surgical tool 240,tool drive 230, and control unit 210. The surgical tool 240 may beattached with the tool drive 230 by bringing complementary or matingsurfaces of their respective housings in contact within one another. Theattaching may also include fastening the housings with one another.Furthermore, one or more sensors (not shown) of the tool drive 230 maybe used by the control unit 210 to detect the attaching, includingreading data from the surgical tool 240 that identifies the surgicaltool 240, indicates which tool disks (e.g., tool disk 244-j) are used tocontrol movements of the end effector 246, includes calibration values,indicates whether the tool has hard stops, or indicates which tool diskscontribute to movement of or are connected by a transmission to othertool disks in the surgical 240. The data may be transferred to thecontrol unit 210 via a communication link (e.g., a wired or wirelesslink) established between a communications interface 318 of the controlunit 210 and sensor readout circuitry (not shown) in the tool drive 230.The data may then be stored in memory 314 as part of an engagementcontrol program (engagement control 316) and may be associated with thatparticular surgical tool 240 so long as the latter remains attached tothe tool drive 230.

The control unit 210 including its programmed processor 312 may beintegrated into the surgical robotic system 100 (FIG. 1 ) for example asa shared microprocessor and program memory within the control tower 103.Alternatively, the control unit 210 may be implemented in a remotecomputer such as in a different room than the operating room, or in adifferent building than the operating arena shown in FIG. 1 .Furthermore, control unit 210 may also include, although notillustrated, user interface hardware (e.g., keyboard, touch-screen,microphones, speakers) that may enable manual control of the robotic armand its attached tool 240, a power device (e.g., a battery), as well asother components typically associated with electronic devices forcontrolling surgical robotic systems.

Memory 314 is coupled to one or more processors 312 (genericallyreferred to here as “a processor” for simplicity) to store instructionsfor execution by the processors 312. In some embodiments, the memory isnon-transitory, and may store one or more program modules, including atool control 320 and an engagement control 316, whose instructionsconfigure the processor 312 to perform the engagement processesdescribed herein. In other words, the processor 312 may operate underthe control of a program, routine, or the execution of instructionsstored in the memory 314 as part of the tool control 320 and engagementcontrol 316 to execute methods or processes in accordance with theaspects and features described herein.

In response to detecting the attaching of the surgical tool 240 with thetool drive 230, engagement control 316 performs (or rather configuresthe processor 312 to perform) a process for detecting the mechanicalengagement of tool disks with corresponding drive disks (which areactuator driven), such as engagement of tool disk 344-i withcorresponding drive disk 334-i. The engagement control 316 may signal(through the tool control 320) that one or more of the actuators of tooldrive 230 impart motion of their respective drive disks. In someembodiments, these instructions or signals include instructions toenergize, activate or otherwise provide power to a motor so that themotor can produce or apply a specific amount of torque, cause the drivedisk to rotate at a specific speed and direction, by applying a certainvoltage command, current command, etc. Furthermore, the motion of eachdrive disk can be controlled to start rapidly initially during theengagement detection process, and then ramp down slowly once engagementis near, or proximity to alignment of mating features is detected or apredetermined time limit is reached without detecting engagement. Forinstance, based on the relative position of a drive disk to a tool disk(which may be based on a known calibration value), the actuator speed isramped down to a predetermined speed (e.g., until the drive disk iswithin a threshold distance of where the mating features become aligned.

The engagement control 316 monitors one or more motor operatingparameters of the motors of actuators of the tool drive 230. Asdiscussed herein, the motor operating parameters can include torqueimparted by a motor, voltage supplied to a motor, impedance as seen onthe input drive terminals of a motor when attempting to drive the motorto move at a certain velocity, motor speed, as well as other motoroperating parameters. One or more of these parameters may be monitoredby comparing them to thresholds, so that when the thresholds are reachedthen a mechanical engagement event is deemed to have occurred (between,for example, tool disk 344-i and drive disk 334-i.) As discussed herein,mechanical engagement is expected to be detected when correspondingmating features of a tool disk and a drive disk align and fasten withone another to that rotation of the drive disk will cause for exampleboth immediate and proportional rotation of the mechanically engagedtool disk (as one with the drive disk.) Such engagement is expected tobe detected when one or more of the motor operating parameters satisfiesa threshold (e.g., reaching or exceeding a threshold indicative of ahard stop being reached, a maximum torque, voltage, or impedance value,a torque, voltage, or impedance value greater than what would be neededto overcome friction that initially appears when the tool 240 is firstattached to the tool drive 230. The engagement control 316 thus infersor deduces that tool disk 344-i and drive disk 334-j have engaged withone another (e.g., fastening of respective disk mating features with oneanother).

Note that engagement control 316 need not monitor sensor readings forall of the motor parameters that are available from the tool drive 230.Instead engagement control 316 could monitor only one or morecharacteristics of interest based on, for example, whether surgical tool240 is subject to any hard stops or physical movement constraints,whether one or more tool disks operate in concert (cooperate with eachother) to impart movement on surgical tool 240, whether tool disksimpart movement on surgical tool 240 via cables or directly (e.g.,through a gear box), or a combination thereof, in order to determinewhen a threshold associated with engagement is satisfied.

In some embodiments, engagement control 316 monitors patterns of motoroperating parameters, such as patterns of torque, voltage, motor speed,impedance, etc. that are the result of drive disk 234-j rotating overtool disk 244-j but without mechanical engagement. That is, a certainamount of torque, force, voltage, etc. could be measured, which isgreater than what is exhibited by a free moving drive disk (where thesurgical tool 240 is not attached to the tool drive 230) and less than amechanically engaged drive disk (when for example mating features of thetool and drive disks pass each other while the tool and tool drivehousings are in contact, but without engaging.) When this motorparameter pattern changes as detected, such as due to a hard stop orphysical motion constraint being encountered, engagement control 316 issaid to have detected mechanical engagement. Monitoring and interpretingpattern based motor operating pattern also enables engagement control316 to detect engagement (between tool disk 344-j and drive disk 334-j)even when no hard stop or motion constraint is available, or withouthaving to drive a drive disk to a tool's hard stop or other motionconstraint.

In some embodiments, when engagement control 316 detects mechanicalengagement of tool disks with drive disks, it may also initiate averification process or engagement check in which the actuators of tooldrive 230 are signaled to undergo a predetermined set of one or moremotions, to verify the detected engagement. For example, the actuatorsmay be instructed to cause their respective drive disks to rotate in adirection opposite to the direction of engagement (the latter being thedirection in which the drive disks were rotating when engagement wasinitially detected, e.g., in the direction of motion 445 seen in FIG.4A). Then, the drive disks may be rotated back in the direction ofengagement until a second engagement is detected (e.g., when aparticular motor parameter reaches a threshold that is consistent withthe tool disk reaching a hard stop or a motion constraint, when aparticular motor parameter reaches a threshold that is consistent withresistance against the rotating tool disk that is not caused by frictionalone (friction between the tool disk and a corresponding drive disk),or a combination thereof.

Engagement control 316, based on having detected engagement of tooldisks to drive disks, or based on a countdown timer having expiredwithout detecting engagement, generates a notification for an operatorof the surgical robotic system. The notification may either indicatethat engagement has occurred so that the surgical tool 240 is ready foruse, or that engagement has not occurred and so the surgical tool 240should be reattached.

FIG. 5A is a flow diagram illustrating a process 500 for engaging asurgical tool with a tool drive of a surgical robotic system, inaccordance with an embodiment of the disclosure. The process 500 may beperformed by a programmed processor (also referred to here as processinglogic), configured according to software stored in memory (e.g., theprocessor 312 and the memory 314 of FIG. 3 , where the processor 312 isconfigured according to the instructions of the tool control 320 and theengagement control 316.)

Referring to FIG. 5A, processing logic begins by activating an actuatorof the tool drive to rotate a drive disk of the tool drive (processingblock 502). For example, processing logic may activate a linear orrotary actuator of a tool drive (e.g., tool drive 230) to turn or rotatethe drive disk (e.g., drive disk 234-j). Furthermore, as discussedherein, when mechanically engaged, the rotation of a drive disk (e.g.,disk 234-j) will cause immediate or direct rotation of a correspondingtool disk (e.g., disk 244-j) of a surgical tool (e.g. surgical tool240).

Processing logic monitors one or more motor operating parameters of theactuator that is causing the rotation of the drive disk while activatingthe motor (processing block 504). In some embodiments, the operatingparameters of the motor being monitored can include torque, motorcurrent, motor velocity, or a combination thereof.

Based on the one or more monitored motor operating parameters,processing logic detects when the drive disk becomes mechanicallyengaged with the tool disk (processing block 506). In one embodiment,the detection occurs when or in response to at least one of the one ormore motor operating parameters being monitored satisfying acorresponding condition or threshold. For example, the condition can beassociated with a value of a motor operating parameter that occurs inresponse to the motor reaching a physical constraint against furtherrotation of the tool disk (e.g., reaching a mechanical limit of a rangeof motion when a physical barrier to the movement is encountered, amaximum degree of movement of the end effector of the tool is reached,opposition with another activated motor actuator occurs, etc.). Asanother example, the condition may represent a motor operating parameterexhibited when there is friction due to the drive disk contacting andsliding against the tool disk during rotation but without the mechanicallatching or fastening of the drive disk to the tool disk. In embodimentsdiscussed herein, when mechanical engagement of the drive disk with thetool disk is detected, one or more additional actions, such asgenerating system or operator notifications, initiating one or moreengagement verification operations, storing reference values, etc. maybe performed by processing logic.

FIG. 5B is a flow chart illustrating a process 550 for detectingengagement of a tool disk with a drive disk based on one or more motoroperating parameters of an actuator that is driving the drive disk. Theprocess 550 is performed by processing logic that may comprise anycombination of hardwired circuitry and programmed processor, where forexample the process 550 may be performed by the processor 312 programmedin accordance with the tool control 320 and engagement control 316described above. The process may begin with detecting that a detachablesurgical tool has been attached to a tool drive of a robotic arm of asurgical robotic system (processing block 552). The attachment may bedetected based on sensors of the tool drive coming within wirelessdetection range or being conductively connected with an informationstorage unit in the detachable surgical tool. As discussed herein, theinformation storage unit may include a tool identifier, and may alsoinclude additional tool attributes, such as which of several availabletool disks in the tool housing are actually connected by a transmissionin the housing to the end effector in the detachable surgical tool, whattype of transmission in the tool controls movement of the end effector(e.g., cable driven, direct drive, etc.), what direction of movement orrotation is allowed, if there are any ranges of such movement orrotation, calibration values (e.g., cable lengths, current cable length,maximum winding, rotational position of tool disks or a home position ofa tool disk, etc.), as well as other tool attributes discussed herein.

At least one motor of the tool drive is then activated causing the atleast one motor to rotate an associated drive disk corresponding to atool disk (that is connected by a transmission in the surgical tool tocontrol motion of the end effector (processing block 554). In oneembodiment, a current to be supplied to the motor, a torque to beachieved by the motor, or a direction of movement is signaled to thetool control 320, so that the motor will cause the drive disk to rotateat a predetermined velocity in a predetermined direction. In otherwords, processing logic causes a signal to be sent to a motor drivercircuit, commanding the motor driver circuit to apply power to orenergize the motor. In some embodiments, the predetermined speed is setbased on a determination, at the time of the detected attachment of thetool drive with the detachable surgical tool, of for example, the typeof tool, tool drive transmission type (e.g., cable driven, direct drive,etc.), type of restraint that will be encountered (e.g., a hard stop, aphysical constraint, opposing motion constraint), or a combination ofsuch factors. One or more motor operating parameters of the at least onemotor of the tool drive are then monitored (processing block 556). Themonitored motor operating parameters may correspond with those beingcontrolled by processing logic to cause motion of the motor (e.g.,torque, speed.)

Returning to FIG. 5B, the processing logic repeatedly checks to seewhether or not an engagement condition has been met, e.g., a monitoredmotor operating parameter has reached a threshold (processing block558.) If so, then a mechanical engagement event is flagged, signifyingthat the drive disk has mechanically engaged with its corresponding tooldisk (processing block 564). As discussed herein, the threshold isindicative of a condition associated with the mechanical engagement ofthe drive disks. For example, mechanical engagement is expected when thetorque, current, or impedance associated with the motor at apredetermined velocity or speed exceeds their values that are associatedthe motor encountering tool drive to tool disk friction alone. Thethreshold may be a value which is greater than the torque, voltage,impedance, etc. needed to overcome such friction. As another example,movement of the end effector may be subject to a physical constraint,such as a maximum range of motion of a joint, a hard stop (e.g., asimposed by a cannula wall), an opposing motion of another drive disk, aswell as other physical constraints. In that case, the speed anddirection of movement of the motor are selected to advance the endeffector or tool disk towards the physical constraint. Then, when thephysical constraint is reached, the monitored torque, current, impedancewill spike to a maximum, while the speed will drop to zero. In thisexample, one threshold may refer to torque or motor current that is setnear its maximum value, and another threshold may refer to velocity thatis set lower than a nominal speed of the motor during rotation of thedrive disk, e.g., substantially zero. Thus, the two thresholds act as acheck against one another to make the detection of engagement morerobust.

In response to the detected engagement of the drive disk with thecorresponding tool disk, the motion of the drive disk is stopped(processing block 566). In one embodiment, when the motion is stopped,one or more reference values associated with that position or state ofthe end effector may be stored for later reference and use. For example,where a physical constraint was used to detect the engagement, an indexvalue of the motor, a rotation count, etc. at that moment can be stored,and used later for re-locating the end effector at or near the physicalconstraint. The physical constraint may be, e.g., maximum cable length,cannula wall, maximum of a range of motion, etc. Furthermore, to preventexcessive tensioning of a cable in the case of a cable driven tool, themotion of the drive disk may be stopped, or the motor deactivated,simultaneously or nearly simultaneously in response to the detectionperformed at block 558.

Once engagement of all of the relevant drive disks (those thatcorrespond to in-use tool disks of the particular surgical tool) hasbeen detected in processing block 567 (where the process described abovein blocks 554-556-558-564-566 may have been performed for eachrespective drive disk) then a notification of tool engagement is thengenerated (processing block 568). The notification may be a visualnotification (e.g., a graphical user interface notification), an audiblenotification (e.g., a tone, sound, etc.), sensory (e.g., a hapticnotification), or a combination of such generated by user interfacehardware of the surgical robotic system.

Returning briefly to processing block 558, when the engagement conditionis not met (e.g., a monitored motor operating parameter does not satisfya threshold such that mechanical engagement of a tool disk and acorresponding drive disk has not occurred), a determination of whether atime or rotation limit has been reached is performed (processing block560). A failure to engage may be due to a broken cable, a tool disk anddrive disk not positioned close enough to each other to allow forengagement, etc.) The time limit may be a predetermined maximum timeinterval (countdown timer value) in which a drive disk is allowed torotate without detecting mechanical engagement with a tool disk.Similarly, the rotation limit may be a number of motor rotationsnecessary to impart one or more full rotations of its respective drivedisk. For example, if the rotation limit is associated with one fullrotation of the drive disk, it is assumed that engagement should occurwithin a single revolution of a drive disk. If the time limit, rotationlimit, or some combination of limits are not reached (processing block560), the monitoring of the one or more motor operating parameter valuescontinues (return to processing block 556.) However, if the one or morelimits are reached (processing block 560), a notification, similar tothe notification of processing block 568, that an error has occurred andtool engagement has failed is generated (processing block 562). In thiscase, an operator of the surgical system may be instructed to detach thesurgical tool from the tool drive, and then reattach them to restart theengagement process of FIG. 5B.

Turning now to FIG. 5C, this is a diagram of a process performed by acontrol unit for engaging a surgical robotic tool with a tool drive, aspart of a surgical robotic system. The system includes the surgicalrobotic tool 240 that is depicted in FIG. 2 , having one or more tooldisks at a proximal end and an end effector at a distal end thereof asshown. A tool drive (e.g., tool drive 230) is mounted at a distal end ofa surgical robotic arm 220 as shown, where the tool drive 230 has one ormore drive disks 234 each driven by a rotary motor within a housing ofthe tool drive. Each drive disk 234 is to be attached to a tool disk 244of the surgical tool 240 to impart motion to the end effector 246.

Staying with FIG. 5C, the process for engaging a tool disk with a drivedisk is performed by a control unit, and in particular by one or moreprocessors of the control unit that are configured to (or programmed to)do so. Operation may begin with detecting that the surgical tool isattached to the tool drive (block 582); this may be done by theprocessor wirelessly or via a wired connection reading an identificationor other attributes of the tool, which has been brought into contactwith the tool drive such that a tool disk comes into contact with acorresponding or respective drive disk. The control unit may thenactuate each drive disk through the rotary motor (block 584), anddetect, during the actuation, that a drive disk is engaged to arespective tool disk (block 586); the drive disk is said to be engagedto the tool disk when a pair of coupling features of the drive disk andthe tool disk (there may be more than one pair, e.g., two as shown inFIG. 4A-FIG. 4C, or more) become interlocked. To detect the engagement,the control unit recognizes sensed changes in motor status (status ofthe actuator, or its motor operating parameters), including that avelocity of the rotary motor drops below a predetermined velocitythreshold and a torque of the rotary motor rises above a predeterminedtorque threshold. The velocity threshold may correspond to a velocity atwhich the motor is substantially stopped, wherein the torque thresholdis a value between i) a minimum torque for the motor to overcome thefriction between the drive disk and the tool disk before engagement andii) a maximum torque for the motor to produce. The changes in motorstatus may be caused by at least one of: the end effector reaching ajoint limit, an external force on the end effector, a motion constraintdue to another motor of the tool drive being activated, and acombination thereof. Depending on the particular surgical tool, theremay be more than one tool disk that is in use for operating the endeffector. In that case, the engagement process described above is alsoperformed for each additional tool disk (which has a corresponding drivedisk in the tool drive.) The process then continues with block 588 wherethe control unit signals for example a user interface subsystem of thesurgical robotic system to report engagement of the surgical tool butonly if all of the tool disks that are in use for the particular toolhave been detected as engaged with their respective drive disks.

In one embodiment, a feedback loop may be used to monitor one or moremotor operating parameters and detect when a threshold has been reached.FIG. 6 depicts a block diagram of a feedback loop used to control thevelocity of a motor of a tool drive using velocity feedback. Thefeedback loop may be implemented in hardware, firmware, software, or acombination thereof. A velocity command is received by a controller 602.Controller 602 may be, for example, a proportional-integral-derivativecontroller (e.g., PID controller 702 of FIG. 7 ) providing aloop/feedback mechanism to provide an appropriate motor current (e.g.,the controller output, ctrlr out) to drive motor/actuator 604 at thevelocity and in the direction of the velocity command (also referred toas velocity setpoint.) For example, the direction may be in a windingdirection of a cable driven tool disk 244-j. As another example, thedirection may be a direction that will oppose the motion of anothermotor whose attached tool disk 244-i should be cooperating with the tooldisk 244-j. As yet another example, the direction may be a directionthat causes the motor to advance the end effector towards a hard stop,such as a physical barrier or a mechanical limit of range of motion. Inone embodiment, the controller 602 may use various values, such asdesired torque to achieve the velocity, current to achieve the velocity,impedance indicative of a velocity, etc. as a measure for generating thecontroller's current output to motor/actuator 604.

A sensor, such as a torque sensor, velocity sensor, or a combination ofsensors, measures the actual velocity of the motor/actuator. The actualvelocity is then provided as feedback back to controller 602, which maycalculate an error based on a disparity between the actual velocity ofthe motor and the commanded velocity. The controller 602 responds to thedisparity by adjusting its controller output, e.g., a motor currentcommand to the motor/actuator 604, a torque to be achieved by themotor/actuator 604, an impedance value, etc. that will cause themotor/actuator 604 to move towards the velocity command or setpoint. Insome embodiments, controller 602 may output a motor operating parameter,such as the torque, current, impedance, velocity, etc., calculated as aresult of executing the feedback loop.

In another embodiment, controller 602 can include a saturation block(not shown) to ensure that the controller output (e.g., a value that iscontrolling the motor current) does not exceed a threshold, e.g. acurrent threshold, torque threshold, impedance threshold. The value usedby or input to the saturation block may be dual-purposed, namely alsoused as the motor operating parameter value supplied to the processor(for purposes of being monitored during the engagement process.)

FIG. 7 depicts a block diagram of a feedback loop that includes acontroller 702 for controlling the velocity of a motor of a tool drive.In one embodiment, controller 702 is a proportional-integral (PI)controller and may be used within controller 602, and may be implementedin part as hardware, firmware, software, or a combination thereof.

A velocity command (e.g., control variable setpoint) is received bycontroller 702. Controller 702 provides a loop/feedback mechanism toadjust and provide an appropriate current (e.g., the controller output)to drive motor/actuator 704 at the velocity and in the direction of thevelocity command/setpoint. For example, the direction may be in awinding direction of a cable driven surgical tool's tool disk. Asanother example, the direction may be a direction that will oppose themotion of another motor of the tool drive. As yet another example, thedirection may be a direction that causes the motor to advance the endeffector towards a hard stop, such as a physical barrier or a mechanicallimit of range of motion. In one embodiment, the controller 702 may usevarious values, such as desired torque to achieve the velocity, currentto achieve the velocity, impedance indicative of a velocity, etc. as ameasure for generating the controller's current output to motor/actuator704.

Adjustments are made to the original velocity command, such as aproportional adjustment (e.g., block k_(p)) to adjust the velocityproportional to an error (e.g., as determined by the feedback), as wellas an integral adjustment (e.g., block k_(i)) to adjust the velocity toaccount for past error integrated over time. The integral adjustment mayfurther be adjusted using a restoring term generated by block kb whichis in feedback loop for anti-windup, to further adjust the value of theintegral adjustment. The integral adjusted value may be further adjustedby block 1/s (e.g., before being added to the proportional setpointadjusted value. In one embodiment, a saturation block may be used incontroller 702 as shown, to ensure that a value controlling the currentsupplied to the motor does not exceed a threshold, e.g. a currentthreshold, torque threshold, impedance threshold, etc. After theadjustments are carried out by the blocks discussed above, and theresulting current command value does not exceed the value set in thesaturation block, the current command (e.g., the adjusted command, whichhas been corrected based on the feedback and PI adjustments) is fed intothe current amplifier, so that the commanded current into the motoractuator 704 can be amplified by a factor. The factor may be fixed,based on properties of the motor/actuator 704, based on feedback fromthe motor/actuator 704, etc. The motor/actuator 704 is activated as perthe amplified current, and feedback (e.g., speed, torque, velocity, etc.as determined by a sensor coupled with a motor) on the velocity responseof the motor/actuator 704 is provided to the feedback loop implementedby controller 702 as shown.

As discussed above, the value used by (or input to) the saturation blockmay be used as the motor operating parameter value supplied to theprocessor for purposes of monitoring during the engagement process,e.g., representing present motor current or present motor impedance.

In another embodiment, the feedback may be used as a motor operatingparameter value supplied to the processor for purposes of monitoringduring the engagement process. Other variables computed in thecontroller 702 (e.g., adjusted and non-adjusted) may be used as amonitored motor operating parameter.

In one embodiment discussed above, two actuators share the load inmoving a surgical tool, such as sharing the load to rotate an endoscope.The surgical tool (e.g., endoscope) may have a rotation joint without anencoder so the position is determined from the angles of the motors oractuators. Without engagement, the rotation angle of the surgical toolcannot be determined. There is no mechanical hard stop on the rotationjoint, so a hard stop may not be used for homing. The rotation joint iscoupled with two motors on the tool driver. In normal operation, thesetwo motors are working cooperatively to drive the rotation joint. Forexample, in teleoperation after engagement and homing, one motor isprimary and controlled in position mode, and the other motor issecondary and controlled in position or current (torque) mode. Bothmotors drive the movement of the surgical tool in the same direction.Before the two motors drive the endoscope rotation joint, the motorshave to be both engaged to the rotation joint, and the endoscope jointangle is calculated (i.e., homed) based on motor joint positions uponcompletion of engaging.

FIG. 2 shows an example surgical robotic system for engagement and/orhoming of motor control in a robotic surgery system. In general, two ormore drive discs 234 are to engage with a respective two or more toolpads or discs 244. The pads may have other shapes than discs, such asbeing plus (“+”) shaped. The example herein uses discs.

The surgical tool 240 is a surgical tool, such as any of the surgicaltools used in medicine or discussed herein. In one embodiment, thesurgical tool 240 is an endoscope. Rather than having scissors, clamps,or other tools, the surgical tool 240 has a camera at the distal end asthe end effector 246. The endoscope shaft is able to rotate 360 degreeswithout a hard stop. Any number of rotations may be possible due tothere being no hard stop or physical restriction on the rotation. Othertools for rotation or other movements may be used.

The robotic surgical tool 240 includes a housing, a shaft, and an endeffector 246 from proximal end to distal end. The tool discs 244 arepositioned in the housing and linked to the end effector 246 (e.g., bycable, rod, and/or other transmission), which is driven by the drivediscs 234 through the tool discs 244 and transmission after properlyengaged.

The rotary tool discs 244 connect to the shaft of the surgical tool 240for rotating the surgical tool 240. Two or more rotatory tool discs 244connect through a transmission to link the tool discs 244 to thesurgical tool 240. Gearing, clutch, cables, belts, and/or other linkagesreceive force, such as rotational force, from two or more tool discs 244to rotate the surgical tool 240. The power to rotate the surgical toolis shared. In one embodiment, both tool discs 244 rotating in a samedirection both contribute to rotating the surgical tool 240 in the sameor an opposite direction. In another embodiment, the transmission linksso that two tool discs 244 rotating in opposite directions rotate thesurgical tool 240 in one of the directions.

The tool drive 230 includes the actuators 238 (e.g., motors) connecteddirectly or through a transmission to the drive discs 234. The actuators238 and drive discs 234 form rotatory motor drives, which are mateable(e.g., engaging coupling features 447 and 448) with the tool discs 244.The drive discs 234 mate with the tool discs 244. The engagement ormating occurs once the surgical tool 240 is connected to the tool drive230.

The sensors 236 are one or more different sensors. For example, thesensors 236 are encoders for detecting position, such as angularposition, of the motor shaft and/or drive discs 234. The encoder mayoutput position information so that a processor may determine a velocityfrom a time derivative of position. As another example, the sensors 236are current sensors (e.g., current sensing resistor in series with amotor input drive terminal) for detection of the amplitude of thecurrent provided to and/or drawn by the actuators 238. Additional,different, or fewer sensors 236 may be provided for each actuator 238,such as providing both current sensors and encoders.

As shown in FIG. 9 , a current source 901 may be provided. The currentsource 901 outputs current to the actuator 238. Based on controlsignals, the current source 901 provides current to move the actuators238 in position, torque (e.g., current) or other modes of control. Theactuators 238 are supplied with current to cause rotation to givenangular positions (position mode) or to move at a given velocity (e.g.,current mode). Other control modes may be used.

In one embodiment shown in FIG. 9 , the current source 901 adds adithering current 902, such as high frequency (e.g., 60 Hz or higher(e.g., 100 Hz)) sinusoidal current. The dithering current 902 is lowamplitude, such as being 10% or less of a maximum current 908. Thedithering current 902 is added to a ramp-up current 900 provided to theactuator 238. The dithering current 902 is added during an initial partof the ramp-up current and removed for completion of the ramping. Inother embodiments, the dithering current 902 is added over other ranges,such as added after initiating the ramp up current and/or removed afterreaching a steady state current 904. The dithering current 902 mayassist in reducing static friction during contact between the tool discs244 and the drive discs 234 for engaging.

The processor 312 of the control unit 210 is configured to detect matingof the rotary tool discs 244 with the respective rotary drives (e.g.,rotatory drive discs 234) by a change in a signal. The engagement of thedrive discs 234 with the tool discs 244 is detected. The drive discs 234under power from the motor or actuators 238 may slide relative to thetool discs 244 until engaged, at which point the tool and drive discs234, 244 rotate together.

The processor 312 is configured to detect the mating from a change insignal or performance of the actuator 238. The signal from the sensor236, such as the current and/or velocity, are used to detect engagement.Once engaged, the signal changes. For example, the velocity drops tozero or below a threshold velocity. As another example, the currentspikes or exceeds a threshold current. In another example, both the lowvelocity and current spike are detected as representing engagement ormating.

Since two or more actuators 238 drive the surgical tool 240 incombination, the change in signal for detecting the engagement may beperformed for both motor drives. For example, the current and/orvelocity for each actuator 238 is monitored to detect mating. The matingfor each actuator 238 to the surgical tool 240 is detected.

Where no hard stop is provided, the actuators 238 may be driven inopposition to each other. The motor drives may attempt to rotate thesurgical tool 240 in opposite directions and/or at different speeds,opposing each other rather than attempting to rotate together. Eachactuator 238 is to drive the surgical tool 240. By operating inopposition to each other, the actuators 238 may attempt to rotate thesurgical tool 240 in opposite directions and/or at different speeds. Thedriving is in position control mode, but current or other modes ofcontrol may be used.

When the initial drive disc 234 mates with the corresponding tool disc244, the signal for that actuator or drive motor may not change much asthis initial drive disc 234 is the only drive rotating the tool. Thecurrent and/or velocity may change due to the resistance in rotating thesurgical tool 240, but the velocity may not change to below the velocitythreshold and/or the current may not spike to be above the currentthreshold. Once the other or later drive disc 235 mates with thecorresponding tool disc 244, the two motor drives are both engaged andattempting to rotate the surgical tool 240 in opposite directions and/orat different speeds. As a result, the velocities for both motors dropbelow the threshold and/or the currents for both motors spike. The motordrives resist each other, acting as mutual hard or soft stops. If themotors have equal strength or power and are rotating at a same speed inopposition to each other, then the velocity drops to zero and thecurrent spikes to the maximum. Where the motors have different power dueto design or tolerance and/or different speeds, a greater velocityand/or lesser current spike may be provided while still being below thevelocity threshold and/or above the current threshold, respectively.

The processor 312 is configured to verify the engagement. After matingis detected, the engagement may be verified. The encoders indicate therotational position of the tool discs 244 once engaged. Since the tooldiscs 244 link to the same surgical tool 240, the tool discs have aknown relative rotation with respect to each other. For example, thetool discs 244 are designed to have the same angle but opposite sign forany given rotational position of the surgical tool 240. In otherexamples, any relative combination of angles may be used. Due to theengagement, the position of the drive discs 234 corresponds to theposition of the tool discs 244. Where the angles at engagement match thedesigned angles, engagement is verified.

The processor 312 is configured to home the rotational angle of thesurgical tool 240. The current rotational angle of the surgical tool 240is determined once engaged. The surgical tool 240 is calibrated so thatthe angles of the rotatory tool discs 244 for each rotational angle ofthe surgical tool 240 are known. Upon engagement, the processor 312determines the rotational angle of the surgical tool based on therotational angles of the engaged rotary drives (e.g., actuators 238,drive discs 234, and/or tool discs 244) as mated. The calibrationrelates the angles of the engaged rotary drives to the angle of thesurgical tool 240. Referring to FIG. 8 , upon completion of engaging,the joint (e.g., tool disc) angles are α1, and α2 respectively when thesurgical tool (e.g., endoscope) is at home (zero) position, θT. Both α1and α2 are pre-calibrated and are measured from the encoder based anglesθ1 and θ2 of two motors M1, M2.

FIGS. 8 and 9 shows another embodiment of detection of engagement fortwo motor drives working to control the same movement of the surgicaltool 240. A combination of position and current control modes are usedto detect the mating from the change in the signal.

The kinematic equation of motion after the engaging may be representedas:

θ = γ * (θ1 − α1)θ1 − α1 = −(θ2 − α2)where, θ, θ1, θ2 − anglesofendoscopejoint, motorM1joint, motorM2jointγ − gearratioαl, α2 − anglesofM1, M2jointsatendoscopezeroposition

This kinematic equation may be used in engagement detection and/orhoming.

In a first step, the motor M2 is set to operation in the positioncontrol mode. The target position is set to be the current position, sothe motor M2 is held steady or in the current location.

In a second step, the motor M1 is set to operation in a current controlmode. As shown in FIG. 9 , the current 900 is ramped up until thevelocity reaches a threshold, represented by the horizontal portion 904of the current 900. The offset from the maximum current 908 for thehorizontal portion 904 and the slope of the ramp-up may beexperimentally determined.

A dithering current 902 is added to the current 900. For example, a highfrequency (e.g., 100 Hz) sinusoidal current provides low amplitudedithering and is superimposed on to the ramp-up current. This highfrequency current helps to overcome the static friction between thediscs 234, 244. The angular velocity 906 of the actuator 238 and drivedisc 234 ramps up and then holds steady based on this current control.The direction of the current command (i.e., rotation direction) isarbitrary. The maximum current limit 908 is set between the maximumcurrent to drive the motor alone and the minimum current to drive thecoupled motor and endoscope. The limit may be experimentally determined.

During this second step, the engagement for the motor M1 is detected.Engagement is detected where the motor M1 never moves—the currentcommand ramps up to the maximum current. This may occur where the tooldisc 244 mates to the drive disc 234 upon connection or placement incontact. Engagement is detected where motor M1 stops before reaching thedesired velocity or after reaching the desired velocity. If the motor M1does not stop after a full rotation detected by an encoder, then thevelocity limit may be reduced (e.g., by ½) and the second step isrepeated. If the second step fails to detect engagement again, then anerror is reported and the process stopped.

In a third step, the motor M1 is set to position mode, and the targetposition is set to the current position, θ1, to hold the motor M1 inplace. In a fourth step, the motor M2 is set to be in current controlmode. The same current profile used in the second step (see FIG. 9 ) isused. The direction of rotation for the current is set to be in theshorter direction towards −(θ1−α1)+α2. The same velocity and/or motionconditions are used to determine whether engagement occurs for the motorM2.

In the second and fourth steps, instead of checking for stops, velocitychange may be used to detect engaging status. Once the engagement isconfirmed, the current command is set to zero immediately and proceedsto the next step.

Velocity close-loop control with current saturation may be used toreplace the current ramp up control in the second and fourth steps. Inthe second step, the motor M1 is set to velocity control mode, and thetarget velocity is set to a predefined value. The direction of thevelocity is chosen arbitrarily. The engagement status is detected wherethe motor M1 stops or there is a sudden jump in motor currentmeasurement. In the fourth step, the motor M2 is set in velocity controlmode, and the target velocity is set to a predefined value. Thedirection of the velocity is in the shorter distance to −(θ1−α1)+α2.

In a fifth step, the motor M1 stays in position control mode, and themotor M2 stays in the current control mode. The joint angles of motorsM1 and M2 are checked to verify that the kinematic equation issatisfied. Complete engagement is confirmed where the angles match todesign angles. If engaging fails twice in a row and/or the verificationfails, then the engagement process may be stopped and an error reported.

After successful engaging, homing may be established. The endoscopejoint angle relative the zero position may be calculated from the motorM1 joint angle using the kinematic equation.

FIG. 10 shows one embodiment of a method for engaging motor control of asurgical tool in a surgical robotic system. The method also includeshoming a rotational position of a surgical tool in the surgical roboticsystem. For example, engagement of an endoscope with tool driver motors(M1, M2) and/or homing are provided. Engaging drives the motors untilboth motor joint shafts are securely coupled with the endoscope shaftthrough key and/or key hole or another coupling. Homing finds a jointangle between the zero position of the endoscope rotation joint and theprimary joint encoder position.

The method is performed by the surgical robotic system of FIGS. 2 and 3or another surgical robotic system. The method is performed where twomotors drive the same motion of the surgical tool, such as rotation in asame direction by an endoscope. A processor of the control unit or othercontroller performs the method upon connecting the surgical tool 240 tothe tool drive 230. Once the identity of the surgical tool 240 isdetermined as one with two or more motors combining power or motion todrive the same movement, the processor performs the engagement detectionand/or homing.

The acts are performed in the order shown or a different order. Forexample, acts 1002 and 1004 are performed simultaneously. As anotherexample, acts 1002 and 1004 are repeated to detect engagement ofdifferent motors. Additional, different, or fewer acts may be provided.For example, acts 1006 and/or 1008 are not provided for detection ofengagement. As another example, acts 1002 and 1004 are not providedwhere other engagement detection is used. In yet another example, act1006 is not provided. In other examples, acts for teleoperation orsurgical use of the engaged and homed endoscope or another surgical toolare provided. In one embodiment, the attachment of the surgical tool tothe tool drive is detected (see acts 552 of FIG. 5B and 582 of FIG. 5C)to then trigger detection of engagement f the discs.

In act 1000, the processor (e.g., controller or control unit) detectsengagement of two or more rotary tool pads or discs 244 with arespective two or more rotary drives (e.g., actuators 238 and drive padsor discs 234). Using releasable (e.g., spring loaded, physical barrier,or friction fit) fittings, the drive discs 234 mate with the tool discs244.

In act 1002, the motors (e.g., actuators 238) rotate. The rotation ofthe motors is performed under position control, but other control modesmay be used. During teleoperation to rotate or translate the surgicaltool in one direction, the two motors rotate in specific directions(e.g., both motors rotate in the same direction or one more rotates inone direction and another motor rotates in a different direction),depending on the transmission or other linkage from the tool discs 244to the surgical tool 240. For engagement, the motors rotate inopposition to each other. For example, an endoscope is rotated clockwiseby rotating one motor clockwise and the other motor counterclockwise. Torotate in opposition to each other, the motors rotate in the samedirection so that one motor attempts to rotate the endoscope clockwiseand the other attempts to rotate the endoscope counterclockwise. Sincethe endoscope is free of a hard stop or physical limiter to rotation,the opposition rotation of the motors that share movement burden resisteach other, acting as stops once engaged.

Due to the motor rotation, the drive discs 234 connected to the motorsdirectly or through gearing rotate. The drive discs 234 are infrictional contact with the tool discs 244. The rotation has sufficientforce to overcome static friction, so the drive discs 234 rotaterelative to the tool discs 244, which are linked to the surgical tool(e.g., surgical tool 240 or endoscope). The rotation should eventuallyresult in engagement of the physical engagement mechanism (e.g.,protrusion and indent, shaped extension and slot, protrusion and stop,and/or snap fit holder and extension) on the tool and drive discs 234,244.

Dithering in current, position, and/or other control modes may be used.By dithering the command signal, static friction may be more easilyovercome so that the drive disc 234 rotates at a greater rate than thetool disc 244 for engagement.

Once both or multiple pairs of tool and drive discs 234, 244 are matedor engaged, then the rotation in opposition acts as a stop. Onceengaged, the force of rotation from each motor transfers through thelinkage or transmission linking the tool discs 234, causing resistancein movement.

In an alternative embodiment, one of the motors is controlled inposition mode to not rotate while the other motor rotates to engage.Once one motor is engaged, the engaged motor drive does not rotate whilethe other motor engages. For example, the steps described above withreference to FIG. 9 are performed.

In act 1004, the processor (e.g., control unit or controller) monitorsfor and detects engagement of the motors (e.g., actuators 238) with therespective tool discs 244. The detection is based on monitoring for achange in performance of the motors. The change may be represented as adifference, such as a difference in performance above a threshold (e.g.,current doubled or increased by over X amount). The change may berepresented as an absolute value relative to a threshold, such as thevelocity transitioning to below a threshold velocity (e.g., velocitygoing to zero) and/or the current transitioning to be above a threshold(e.g., current spiking).

Once the performance change using one or more parameters (e.g., bothcurrent and velocity) for each of the motors occurs, then engagement isdetected. Engagement may be detected as engagement by all or a sub-setof the motors. Once the performance characteristic of each of the motorsor each of the sub-set of motors changes, engagement of the surgicaltool is detected. Alternatively, engagement is detected separately foreach motor. Once all the desired motors are engaged, the engagementprocess ends.

In act 1006, the processor (e.g., controller or control unit) checks orverifies engagement. Once engagement is detected, a check is performedto verify proper engagement. The check relies on the transmission orlinkage between the tool discs 244 and the surgical tool 240. Since bothtool discs 244 drive the same motion, the angle of the tool discs 244 toeach other is fixed or within a tolerance range. The mechanism forengaging has a fixed orientation on the tool discs 244 and drive discs234, so the engaged tool discs 244 have that fixed orientation whereboth are engaged. The angles of the drive discs 234 and correspondingmotor shafts are measured by the sensor 236 (e.g., encoder). Due toengagement, the angles correspond to the angles of the tool discs 244.

The angles of rotation are compared. Where the expected angles or anglesof rotation within a threshold are detected, the engagement is verified.For example, the transmission or linkage between the tool discs 244 isdesigned to have the same angle with opposite signs for any rotationalposition of the surgical tool 240 (e.g., endoscope). Once engaged, therotatory position of the motors and drive discs 234 have the same angle(e.g., same absolute angle with different signs). Other anglecombinations may be used.

In act 1008, the processor (e.g., controller or control unit) determinesa current rotation angle of the surgical tool once engaged. This homingdetermines a rotation angle of the medical instrument upon theengagement.

The rotation angle is determined from the angles of the motors andrespective drive discs 234. Once engaged, the angles of the drive discs234 from the sensors 236 are the angles of the tool discs 244. A look-uptable or other function from calibration maps the angles of the tooldiscs 244 (and/or drive discs 234) to the angle of the surgical tool.The transmission relates the tool disc 244 angles to the surgical toolangle or position, and the calibration measures the relationship. Oncethe angles for the discs 234, 244 for each of the motor drives isdetermined, the calibration is used to find the angle of the surgicaltool 240.

The engagement and/or homing process then ends. If engagement is notdetected in act 1000, engagement is not verified in the check of act1006, and/or homing of act 1008 fails, the process for engagement isrepeated or a different engagement process may be performed. If multiplefailures occur, then an error message is sent. Where engagement and/orhoming are performed successfully, then the surgical tool 240 and motordrives are ready for teleoperation in surgery.

The above description of illustrated embodiments of the invention,including what is described below in the Abstract, is not intended to beexhaustive or to limit the invention to the precise forms disclosed.While specific embodiments of, and examples for, the invention aredescribed herein for illustrative purposes, various modifications arepossible within the scope of the invention, as those skilled in therelevant art will recognize. For example, although FIG. 4A-FIG. 4Cdepict a surgical tool 240 that has a cable-driven transmissionconnecting the tool disk 244 to the end effectors (not shown), theengagement process described above is also applicable to other types ofsurgical tools having different transmissions (not necessarilycable-driven.) These modifications can be made to the invention in lightof the above detailed description. The terms used in the followingclaims should not be construed to limit the invention to the specificembodiments disclosed in the specification. Rather, the scope of theinvention is to be determined entirely by the following claims, whichare to be construed in accordance with established doctrines of claiminterpretation.

What is claimed is:
 1. A method for tool engagement in a surgicalrobotic system, the method comprising: detecting a mechanical attachmentof a surgical tool to a tool drive, the tool having a first tool discand a second tool disc to be engaged with a first drive disc and asecond drive disc, respectively, of the tool drive, the first and secondtool discs linked to an end effector of the surgical tool; actuating thefirst drive disc by a first motor and the second drive disc by a secondmotor of the tool drive such that the first and the second drive discsrotate in opposition to each other; monitor performance of the first andthe second motors; and detecting engagement of the first and second tooldiscs with the first and second drive discs based on detecting a firstvelocity of the first motor or a second velocity of the second motor isbelow a velocity threshold.
 2. The method of claim 1 wherein actuatingcomprises actuating the first and second drive discs by the first andsecond motors with position control mode.
 3. The method of claim 1wherein actuating the first and second drive discs comprises the firstand second motors turning in a same direction where a link between thefirst and second tool discs to the end effector uses rotation of thefirst and second tool discs in opposite directions to rotate the endeffector in a same direction.
 4. The method of claim 1 wherein themovement of end effector of the surgical tool comprises rotation of anendoscope free of a hard stop.
 5. The method of claim 1 whereindetecting engagement is further based on detecting non-existence of arepeating torque spikes in, or spikes in currents to the first andsecond motors.
 6. (canceled)
 7. The method of claim 1 further comprisingchecking that a first rotation angle of the first tool disc upon theengagement is within a threshold amount with an opposite sign as asecond rotation angle of the second tool disc upon the engagement. 8.The method of claim 1 further comprising determining a rotation angle ofthe surgical tool upon the engagement from first and second angles ofthe first and second motors while in the engagement with the first andsecond tool discs.
 9. The method of claim 8 wherein determiningcomprises determining the rotation angle based on a calibration.
 10. Asurgical robotic system for engagement, the system comprising: asurgical effector connected by a transmission to first and second rotarytool pads, the surgical effector connected such that rotation of thefirst and second rotary tool pads rotates the surgical effector; a tooldrive having first and second rotary drives mateable with the first andsecond rotary tool pads, respectively; and a processor configured todetect mating of the first and second rotary tool pads with the firstand second rotary drives, respectively, as a change in a signalrepresenting a speed of the first rotary drive or a speed of the secondrotary drive dropping below a speed threshold.
 11. The surgical roboticsystem of claim 10 wherein the surgical effector comprises an endoscoperotatable about a longitudinal axis.
 12. The surgical robotic system ofclaim 10 wherein the first rotary tool pad is driven by the first rotarydrive to rotate in a first direction while the second rotatory tool padis driven by the second rotary drive to rotate in a second directionthat is opposite the first direction, resulting in the surgical effectorrotating in only one of the first direction or the second direction. 13.The surgical robotic system of claim 12 wherein the processor isconfigured to drive both the first and second rotary drives in positioncontrol mode.
 14. The surgical robotic system of claim 10 furthercomprising first and second encoders connected with the first and secondrotary drives, and the speed threshold is within a threshold amount ofzero.
 15. The surgical robotic system of claim 10 further comprisingcurrent sensors connected to detect currents to the first and secondrotary drives, the processor configured to detect first and secondcurrents for the first and second rotary drives spiking, and detect themating further based on detecting non-existence of repeating spikes inthe first and second currents.
 16. The surgical robotic system of claim10 wherein the processor is configured to verify the mating by comparinga first rotational angle of the first rotary drive to a secondrotational angle of the second rotary drive.
 17. The surgical roboticsystem of claim 10 wherein the processor is configured to determine arotational angle of the surgical effector based on rotational angles ofthe first and second rotary drives as mated to the first and secondrotary tool pads.
 18. The surgical robotic system of claim 10 furthercomprising a current source configured to apply a dithering current to acurrent ramp in current control mode to the first rotary drive, whereinthe processor is configured to detect the mating from the change in thesignal from the first rotary drive while in the current control mode.19.-21. (canceled)